1. Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device in which interconnection lines are disposed in a predetermined region of an encapsulation substrate.
2. Description of the Related Art
Among flat panel display devices (FPDs), the organic light emitting display device, or organic light emitting diode (OLED) display device, has attracted much attention as the next generation FPD. Because the OLED display device is a self-emissive display device, it has advantages of a wide viewing angle, a fast response time, and a high contrast, and can be fabricated with a small thickness at low cost. In such an OLED display device, electrons and holes (or carriers) in a semiconductor form pairs to make a transition from an excited state to a ground state, thus emitting light. The OLED display device can be classified into a passive matrix OLED (PMOLED) display device and an active matrix OLED (AMOLED) display device depending on its driving method.
FIGS. 1A, 1B, and 1C respectively show a plan view of a substrate, a bottom view of an encapsulation substrate, and a cross-sectional view of a display device in a conventional OLED display device. The substrate may be considered a front substrate while the encapsulation substrate may be considered a back substrate.
Referring to FIG. 1A, a display region 150 including predetermined pixels is disposed on a substrate 100. A common power supply line 110 is disposed adjacent to the display region 150 and is used to apply a power supply voltage to common power lines 160. The power supply voltage is typically referred to as Vdd in the literature. The common power lines 160 are electrically connected to the common power supply line 110 and used to apply a voltage to each of the pixels. A scan driver 140 outputs a selection signal, and a data driver 130 outputs a data signal. The common power lines 160 are electrically connected to top and bottom portions of the common power supply line 110 and receives power.
Also, a cathode electrode 120 is arranged over the display region 150. A cathode power supply line 170 is disposed on one side of the display region 160 and overlaps the cathode electrode 120. The cathode power supply line 170 is used to apply a cathode voltage to the cathode electrode 120.
Other interconnection lines including the common power supply line 110 and the cathode power supply line 170 are electrically connected to a pad 180 and receive predetermined power.
As described above, a number of interconnection lines are arranged on the substrate 100 so that the display region 150 is reduced by the area occupied by the interconnection lines (hereinafter referred to as a “dead space”). Further, as the OLED display device includes more varied and complicated functions, it needs more interconnection lines. Therefore, it is important to reduce the dead space in order to expand the display region 150 or downscale the display device. In some cases, the interconnection lines are formed with a small width to scale down the display device. However, this method leads to an increase in voltage drop along the line due to increased resistance of the narrower line, which results in an increase in the product of current and resistance (IR) or the voltage drop.
FIG. 1B shows a bottom surface of an encapsulation substrate 101, and FIG. 1C shows a cross-section taken along the line I-I′ of FIGS. 1A and 1B. In FIGS. 1B and 1C, a peripheral portion 190 refers to a region of the encapsulation substrate 101 that is bonded to the substrate 100 using an adhesive 102 coated on the substrate 100. A space over the substrate 100 is hermetically sealed by the encapsulation substrate 101 and may contain a moisture absorbent material (not shown) to protect organic light emitting diodes (OLEDs) 103 disposed on the substrate 100. In particular, the moisture absorbent material may be provided on the bottom surface, i.e. the internal surface, of the encapsulation substrate 101.